Stability in vehicle rolling and pitch depends on the strength of a part ranging from a bead portion to a sidewall portion of a pneumatic tire. Particularly, in a tire for a large-size vehicle compared with a vehicle for a passenger car, a sidewall portion located between a bead portion to a tread portion grounding a road surface is long, and is subjected to a heavy load. Thus, bending deformation is likely to occur in a sidewall portion falling outside in the width direction of a tire at a base point where a bead portion contacts a rim flange, thereby deteriorating the stability in rolling and pitch compared with a tire for a passenger car.
To solve the above problem, the applicants have proposed measures to prevent a bending deformation (see Patent Literature 1). The patent document 1 has disclosed a pneumatic tire comprising a carcass having a carcass body composed of a ply formed of a plurality of carcass cords, covered with a rubber material, toroidally extending between a pair of bead cores, and the carcass folded-back portion that the carcass body wound around the bead core from inside toward outside of the tire and extended outside in the tire radial direction, wherein the rigidity of a bead portion is enhanced by providing a filling material called a stiffener with a 100% elongation modulus greater than that of a rubber material and a rubber with JIS A hardness of 50 degrees to 85 degrees between the carcass body and the carcass folded-back portion (see Patent Literature 1).